Researchers clone pigs

Work could advance research into using pig organs in humans

WASHINGTON (CNN) -- Separate groups of researchers have reported success cloning pigs -- work that could eventually help scientists develop ways to use pig organs for transplant in humans.

Researchers working together in Japan and New York reported in Wednesday's issue of the journal Science that they had cloned a pig named Xena.

Also Wednesday, the researchers who cloned Dolly the sheep
introduced five cloned pigs in the journal Nature. The pigs were born in Blacksburg, Virginia in March. They were cloned using a double nuclear transfer method similar to the technique used to get Dolly.

Xena was cloned with a method called "microinjecting," the scientists in Japan and New York reported. The technique involves injecting genetic material from fetal pig skin cells into eggs stripped of their own genetic material. The researchers said this is a way of getting more specific genetic material into an egg than the method used on Dolly.

Neither method is perfected yet. Researchers implanted 72 embryos to get the five piglets born in March, and Xena was the only pig born out of more than 100 cloning attempts.

Cloning pigs has become a scientific goal because pig organs hold the promise of possibly alleviating the shortage of human organs available for transplantation.

Currently pig livers are sometimes considered for transplant when a patient is in liver failure and there is no human organ available. In such cases, the pig liver is used as a bridge to transplantation, buying the patient time until a human liver can be found.

If pigs could be genetically modified to reduce the risk of organ rejection, it might be possible to use their organs for permanent transplants, not just temporary ones, many scientists believe. Being able to clone pigs would make it easier to raise animals with organs suitable for transplants.
But the issue of using pig organs in humans is controversial. Many researchers worry that pig diseases could be transferred to humans during such procedures.

Also in Wednesday's edition of Nature, Dr. Daniel Salomon of the Scripps Institute reported that certain viruses unique to pigs can infect human cells. He said while scientific technology may make it possible to transplant animal organs into humans, significant safety concerns still exist.

While the pig is not necessarily genetically close with humans, the
functions of the organs are very similar. Pig hearts, kidneys and lungs may also become viable candidates for transplants if the technique is perfected.